The DNA at the ends or telomeres of the chromosomes of eukaryotes usually consists of tandemly repeated simple sequences. Telomerase is a ribonucleoprotein enzyme that synthesizes one strand of the telomeric DNA using as a template a sequence contained within the RNA component of the enzyme. See Blackburn, E. H. (1992) Annu. Rev. Biochem. 61:113-129, incorporated herein by reference.
The RNA component of a mammalian telomerase has not been reported in the scientific literature to date, although, human and mouse telomerases are known to synthesize telomeric repeat units with the sequence 5'-TTAGGG-3'. See Morin, G. B. (1989) Cell 59:521-529; Morin, G. B. (1991) Nature 353:454-456; Prowse, et al. (1993) PNAS 90:1493-1497, incorporated herein by reference. This knowledge has not been sufficient to enable the isolation and identification of the remainder of the nucleotide sequence of the RNA component of either of these telomerases. The RNA component of the telomerase enzymes of Saccharomyces cerevisiae, certain species of Tetrahymena, as well as that of other ciliates, such as Oxytricha, Euplotes and Glaucoma, has been sequenced and reported in the scientific literature. See Singer, M. S. and D. E. Gottschling (1994) Science 266:404-409; Lingner et al. (1994) Genes & Development 8:1984-1988; Greider, C. W. and E. H. Blackburn (1989) Nature 337:331-337; Romero, D. P. and E. H. Blackburn (1991) Cell 67:343-353; Shippen-Lentz, D. and E. H. Blackburn (1990) Science 247:546-552. The teachings of each of these references are incorporated herein by reference. The telomerase enzymes of these ciliates synthesize telomeric repeat units distinct from that in mammals.
There is a great need for more information about mammalian telomerase. Despite the seemingly simple nature of the repeat units of telomeric DNA, scientists have long known that telomeres have an important biological role in maintaining chromosome structure and function. More recently, scientists have speculated that loss of telomeric DNA may act as a trigger of cellular senescence and aging and that regulation of telomerase may have important biological implications. See Greider, C. W. (1994) Curr. Opin. Genetics Devel. 4:203-211; Harley, C. B. (1991) Mutation Res. 256:271-282; Harley, C. B. et al. (1990) Nature 345:458-460, incorporated herein by reference.
Methods for detecting telomerase activity, as well as for identifying compounds that regulate or affect telomerase activity, together with methods for therapy and diagnosis of cellular senescence and immortalization by controlling telomere length and telomerase activity, have also been described. See PCT patent publication No. 93/23572, published Nov. 25, 1993, incorporated herein by reference.
Significant improvements to and new opportunities for telomerase-mediated therapies and telomerase assays and screening methods could be realized if nucleic acids comprising the RNA component and/or encoding the protein components of telomerase were available in pure or isolated form and the nucleotide sequences of such nucleic acids were known.